A revolution is occurring in the design of avionics systems for commercial air transports. The classic avionics system has a federated architecture. It consists of a set of functions, each of which is implemented in one or more Line Replaceable Units (LRUs). This federated architecture is being replaced by an integrated architecture that combines multiple functions into fewer LRUs. Integration offers many benefits, including: lower weight, lower power consumption, increased reliability, less frequent maintenance and greater flexibility. But precisely because functions share hardware resources, greater care must be taken to ensure they will operate correctly, even if co-resident functions fail. This is the engineering challenge of integrated architectures.
While prior art media access protocols have included strict time division multiple access protocols and table driven proportional access protocols, these systems have proven unsatisfactory since functions routing through the bus may conflict. Typically this has been resolved by allowing the functions to "arbitrate" their priority. However, in order to determine priority, the functions must transmit priority information, along with time window and storage memory address information, along with the actual data message. This increases the message size needed by any one function. It would be useful to have a protocol system that does not require the inclusion of additional address, time window, or priority information.